1. Field of the Invention
The present invention is related to sensors applied to the body for monitoring or making measurements of body tissue conditions, metabolism or other body functions indicative of health. More specifically, the present invention is directed to a pulse oximetry sensor which can be readily attached and reattached to a portion of the body in a non-invasive manner.
2. State of the Art
In the prior art, a non-invasive pulse oximetry sensor may be used to measure the relative oxygen saturation of the blood. Typically, in such prior art types of oximetry sensors a light source, such as a light emitting diode (LED) is used to alternately direct light of two different wave lengths, such as red and infra-red light, to the blood through the skin. The light transmitted or reflected by the blood at the different wave lengths can be then compared to provide a measurement of oxygen saturation of the blood.
A typical prior art probe system contains the light emitting sources, such as the LED's, and a light sensor, such as a photo diode, mounted on the appendage of the body, such as a finger, toe, ear lobe, nose, hand, tongue or foot. However, such devices need to be capable of being readily attached to the body appendages, comfortable when attached to a patient, reusable on the same patient, and relatively inexpensive to manufacture.
One type of prior art type oximetry sensor uses the mechanical clamping action of spring biased jaws to retain the sensor on an appendage of a patient. Such a device is illustrated in U.S. Pat. Nos. 4,685,464 and 5,438,986. While such devices are effective, they are inherently difficult to clean and inappropriate for the long term use or application on a patient.
Another type of oximetry sensor relies upon a deformable member being located in the device to retain the sensor on the appendage of a patient. Such a device is illustrated in U.S. Pat. Nos. 4,865,038, 4,928,691, and 5,217,012. During the reuse of such sensors on a patient since the retaining member has been deformed and has a memory, reinstallation of the sensor may affect the comfort of the patient. Also, such sensors are also relatively expensive to manufacture as the sensors contain a number of components.
In yet another type of oximetry sensor in an effort to facilitate reuse of the sensor and to provide comfort to the patient during use of the sensor, the sensor is retained on the finger of a patient through the use of hook and loop fabric. However, such sensors have used complex shapes of hook and loop fabric as retaining devices thereby causing the manufacturing expense of the device to increase. Such sensors are illustrated in U.S. Pat. Nos. 4,825,879, 5,209,230, and 5,469,845.
In another type of oximetry sensor, adhesive is used to attach the sensor to a patient in an attempt to lower manufacturing cost of the sensor, provide comfort to the patient during use of the sensor, and provide a secure attachment of the sensor to the patient. However, since the device must be frequently repositioned on a patient, the adhesive loses its adhesive quality during reuse. Also, the adhesive may irritate the patient during use thereby causing discomfort. Such sensors are illustrated in U.S. Pat. Nos. 4,830,014 and 5,170,786.
In yet another type of oximetry sensor, an elastomeric member is used to retain the sensor on the finger of a patient. Although this allows reuse of the sensor, the degree of pressure applied by the elastomeric member and the elastomeric member being in contact with the skin may cause discomfort to a patient. Such a sensor is illustrated in U.S. Pat. No. 5,337,744.
Since the prior art sensors are generally either reusable and expensive to manufacture, or are not easily reusable and have a relatively low manufacturing cost, or reusable and cause discomfort to the patient, there is a need for a comfortable, extended life, disposable, low manufacturing cost pulse oximetry sensor.